The present invention is related to a method for adjusting the inductance of an inductor, and especially to a method for adjusting the inductance of an inductor without needing a gap spacer.
As shown in FIGS. 1a and 1b, a conventional inductor 10 includes a bobbin 20, a U-shaped magnetic core member 30, an I-shaped magnetic core member 50, and a spacer 60. Several rounds of wires are wound on the bobbin 20 to be employed as a coil of the inductor 10. Because the magnetic core of the inductor 10 is constituted by the U-shaped magnetic core member 30 and the I-shaped magnetic core member 50, this inductor 10 is commonly called a xe2x80x9cUI inductorxe2x80x9d. The U-shaped magnetic core member 30 has a concavity 35 on a side wall thereof. The U-shaped magnetic core member 30 is engaged with the bobbin 20 but the opening of the central hole of the bobbin 20 is exposed out of the concavity 35 of the U-shaped magnetic core member 30. The spacer 60 is disposed between the adjacent magnetic core members 30, 50 to space the core members out of contact with each other, thereby reducing magnetic interference therebetween. The spacer 60 may be made of a non-magnetic material, such as plastic, aluminum or paint, which does not cause any magnetic interference between the two magnetic core members 30, 50 and the two magnetic core members 30, 50 may be fixed and held through the spacer 60 with a certain space therebetween. Typically, this spacer 60 is made of an insulating material and adhered to one end of the I-shaped magnetic core member 50. The end of the I-shaped magnetic core member 50 with the spacer 60 is inserted into the central hole of the bobbin 20 through the concavity 35 for allowing the spacer 60 to be attached to the U-shaped magnetic core member 30 so as to assemble the inductor 10 as shown in FIG. 1a. Briefly, the function of the spacer 60 is to form a gap between the I-shaped magnetic core member 50 and the U-shaped magnetic core member 30 so that the inductance of the inductor 10 can be changed by adjusting the spacer size.
However, when manufacturing such an inductor, there exists some problems as follows.
(1) When the I-shaped magnetic core member 50 is inserted into the hole of the bobbin 20, the spacer 60 may be adhered to the inner wall of the central hole of the bobbin 20 due to its adhesive property. If the I-shaped magnetic core member 50 is forcedly inserted into the bobbin 20, the spacer 60 may be deformed, thereby influencing the thickness of the spacer 60 and generating an error of the gap, so that the predetermined inductance can not be obtained.
(2) It is uneasy to precisely control the length of the I-shaped magnetic core member 50 inserted into the bobbin 20.
(3) One end of the I-shaped magnetic core member 50 is attached to the U-shaped magnetic core member 30 only through the spacer 60. When manufacturing the inductor, the gap may become larger because of the thermal expansion of the spacer so that the inductance of the inductor may be changed.
(4) If the gap is too large or the spacer 60 is too thick, the other end of the I-shaped magnetic core member 50 will be protruded over the edge of the bobbin 20, or even over the pin 70 of the bobbin 20, after inserting the I-shaped magnetic core member 50 into the central hole of the bobbin 20.
(5) The size of the spacer 60 must be matched with that of the central hole of the bobbin 20. If the size of the spacer 60 is too big, the I-shaped magnetic core member 50 can not be smoothly inserted into the central hole of the bobbin 20. If the size of the spacer 60 is too small, the spaced area between the I-shaped magnetic core member 50 and the U-shaped magnetic core member 30 may be insufficient.
Therefore, it is desirable to develop a method for adjusting the inductance of an inductor without needing a gap spacer so as to solve the above-described defects.
An object of the present invention is to provide a method for adjusting the inductance of an inductor.
Another object of the present invention is to provide a method for adjusting the inductance of an inductor without needing a gap spacer.
The inductor at least includes a bobbin with at least one round of wire wound thereon, a first magnetic member having a concavity on a side wall thereof, and a second magnetic member having a protrusion at a first end thereof for allowing the second magnetic member to be partially inserted into the bobbin through the concavity of the first magnetic member. According to the present invention, the method includes the steps of selecting a reference piece with a suitable thickness to be disposed between the protrusion of the second magnetic member and the side wall of the first magnetic member with the concavity and closely attached to both of them as the second magnetic member is inserted into the bobbin, and partially removing the second magnetic member from a second end thereof according to the thickness of the reference piece so as to obtain a predetermined inductance value.
In addition, the method further includes a step of determining whether the inductance of the inductor is identical to the predetermined inductance value after the reference piece is disposed between the protrusion of the second magnetic member and the side wall of the first magnetic member and the second magnetic member is partially inserted into the bobbin. The thickness of the reference piece can be changed if the inductance of the inductor is not identical to the predetermined inductance value.
Preferably, the first magnetic member is a U-shaped type magnetic core member and the second magnetic member is an I-shaped type magnetic core member. The first and second magnetic members can be made of one selected from a relatively soft magnetic material, Mnxe2x80x94Zn ferrite, Nixe2x80x94Zn ferrite and a silicon steel plate, respectively, and employed as a magnetic core of the inductor.
Preferably, the second magnetic member is shortened by polishing the second end thereof.
The reference piece is used for forming a gap between the second end of the second magnetic member and another side wall of the first magnetic member opposed to the side wall of the first magnetic member with the concavity. The height of the reference piece is greater than that of the side wall of the first magnetic member with the concavity to prevent the second magnetic member from being completely inserted into the bobbin. Certainly, the reference piece is removed before the inductor is assembled.
Preferably, the protrusion of the second magnetic member has a recess formed on an upper surface thereof for inserting a tool therein to grab the second magnetic member.
The present invention may best be understood through the following description with reference to the accompanying drawings, in which: